.sevenb .shape.a {
    top: calc(50% - 2em);
    left: calc(50% - 9em);
    transform-origin: 10em 50%;
    animation: sevenb 3s infinite linear;
}
.sevenb .shape.b {
    top: calc(50% - 1em);
    left: calc(50% - 1em);
    width: 2em;
    height: 2em;
    background: yellow;
    animation: sevenb 6s infinite linear reverse;
}
@keyframes sevenb {
    100% {
        transform: rotateZ(360deg)
    }
}